Field of the Invention
The present invention relates to image capturing apparatuses and control methods of the same.
Description of the Related Art
Recently, the number of pixels in image sensors is on the increase due to the miniaturization of pixels, which has enabled high-resolution images to be captured. Even consumer image capturing apparatuses usually have 10 million to 50 million pixels.
However, the capacity of a signal transfer circuit for transferring signals from an image sensor to a signal processor is fixed, and thus, an increase in the number of pixels in the image sensor relatively lengthens the time taken to transfer image signals from all pixels. FIG. 9 shows a typical configuration of an image sensor and an image processor, and an image processor 900 performs various kinds of signal processing on an image signal that is output from an image sensor 901. The image sensor 901 includes a pixel unit 902 that includes a photoelectric conversion element, an AD conversion unit 903 for converting an image signal that is read out from the pixel unit 902 into a digital signal, and a P/S conversion unit 904 for performing parallel/serial conversion on the image signal that has been converted into a digital signal by the AD conversion unit 903.
To increase the speed of reading out image signals with the above configuration, the speed of reading out image signals from the image sensor 901 to the image processor 900 needs to be increased. For example, even if the image sensor 901 has 24 million pixels, the data volume of each pixel is 12 bits, the frame rate is 120 fps, and data is transferred through eight ports between the P/S conversion unit 904 and the image processor 900, a communication capacity of 4.32 Gbps is required. However, it is difficult to realize such high-speed data transfer due to constraints such as power consumption in circuits, heat generation in transfer circuits and processing circuits, and data transfer accuracy. To address this, Japanese Patent Laid-Open No. 2015-136093 describes a configuration in which image signals are read out from an image sensor at high speed by providing the image sensor with a frame memory for storing image signals from all pixels.
During simple reproduction (quick review) after shooting a still image, image signals are transferred from the image sensor 901 to the image processor 900, development processing is performed by the image processor 900, and image data is output to a display unit (not shown). In this case, the speed of reading out image signals from the image sensor 901 to the image processor 900 may be a factor that inhibits improvement of system performance.